import Monad

class Applicable a b c | a b -> c where
  apply :: a -> b -> c

instance Applicable a (a -> b) b where
  apply x f = f x
instance Applicable (a -> b) a b where
  apply f x = f x
instance (Monad m, Applicable a b c) => Applicable (m a) (m b) (m c) where
  apply = liftM2 apply

int :: Int -> Int
int = id
plus :: Int -> Int -> Int
plus = (+)

--test = apply [int 3] (apply [plus] [int 5])